Method of separating peat into fibrous substance and humic substance

ABSTRACT

Method of separating peat into its fibrous component and humic component comprising mining peat in the water existing in a peat bed to form a peat slurry, disintegrating it to suspend the fibrous component and humic component in the water, and separating the fibrous component from the humic component suspended in the water.

United States Patent Masao Hirota Sunagnwa, Hokkaido;

Kazuml Nakarni, Sunagawa, Hokkaido; Kenji lo, Sunagawa, Hokkaido; Keiji Tanaka, Sunagawa, Hokkaido; Katsuji Matsuda, Tokyo, all of, Japan Aug. 8, 1969 Sept. 7, 1971 Mitsui Toatsu Chemicals, Incorporated Tokyo, Japan Dec. 30, 1968 Japan [72] Inventors App]. No. Filed Patented Assignee Priority [54] METHOD OF SEPARATING PEAT INTO FIBROUS SUBSTANCE AND HUMIC SUBSTANCE 2 Claims, 2 Drawing Figs.

[52] U.S. Cl 299/9,

[51] Int. Cl E2lc 49/00 [50] Field of Search ..299/9; 37/3; 44/27-31 [56] References Cited UNITED STATES PATENTS 962,l20 6/1910 Bradley 37/3 1,038,565 9/1912 Granville 37/3 1,476,407 12/1923 McDougall 44/29 Primary ExaminerErnest R. Purser Attorney-Christen & Sabol ABSTRACT: Method of separating peat into its fibrous component and humic component comprising mining peat in the water existing in a peat bed to form a peat slurry, disintegrating it to suspend the fibrous component and humic component in the water, and separating the fibrous component from the humic component suspended in the water.

PATENTED SEP 119?: 3603643 sum 2 or 2 METHOD OF SEPARATING PEAT INTO FIBROUS SUBSTANCE AND HUMIC SUBSTANCE This invention relates to a method of separating peat (including grass peat and forest peat) into a fibrous substance and a humic substance which are its components.

Naturally existing peat is formed of a fibrous part, a colloid fine grain part (humic substance) rich in organic substances and a large amount of water. As the greater part of this water is contained in the humic substance, it has been very difficult to remove water from mined peat. For example, even with dehydration by compression or centrifugal separation, it is not easy to dehydrate peat. Furthermore, since peat has been mined mostly by manpower the mining cost per unit weight of the dry product is high and due to the characteristic of peat beds that the underground water level is high, it-has been almost impossible to deep mine it. 1

Heretofore, many attempts have been made to utilize peat for various uses, for example, the production of fertilizers by the reaction or mixing of peat with fertilizing substances and the utilization of peat as a soil-conditioning material, deodorant and feed-absorbing material. However, peat is best utilized when the fibrous component and humic component are separated instead of using the peat as it is. Thus, the respective characteristics of the components can be utilized and more valuable products can be obtained.

An object of the present invention is to provide a method of making peat effectively more utilizable.

Another object of the present invention is to provide an efficient method of mining peat and separating it into its fibrous component and its humic component.

Other objects and advantages will be obvious in light of the appended drawings, in which:

FIG. 1 is a diagrammatic elevational view illustrating apparatus by which the method of this invention is employed; and

FIG. 2 is a diagrammatic isometric view illustrating apparatus used in the separating operation of this invention.

According to the present invention, there is provided an improved method of separating peat into its fibrous component and its humic component comprising mining the peat in the water existing in the peat bed to form a peat slurry, disintegrating the peat slurry into a fibrous component suspension and a humic suspension in the water, separating said fibrous component from the humic component suspension with a screen.

A pump dredger can be used to mine peat in water by placing the pump dredger on the peat bed after the surface soil has been removed, for example, with a drag line. The peat is cut into small blocks with the cutter of the pump dredger. The peat blocks are taken out to the upper part of the dredger between the cutter and its shaft. These small blocks are sucked into a pump together with water in the peat layer and are agitated by the impeller of the pump to disintegrate the blocks into a suspension of the fibrous and humic components. At the same time, the peat and water are hydraulically conveyed. Usually the peat is well disintegrated in the pump. However, if necessary or desired, a beater can be provided before or after the pump to beat the peat and further disintegrate it into the fibrous and humic components. When the hydraulic conveyance is used, the concentration of peat (all solid components) in water is preferably about 1 to about 5 percent by weight.

The mining operation shall be explained with reference to FIG. 1. A pump ship 1 is rotatably connected to a stay or pylon 2 and is freely rotatable around the stay 2 as the pivot point. Pump ship 1 is so connected to stay 2 that it can be pulled in the direction of the bow by pulling wire rope 4 which is anchored to stay or anchor 3. At the forward end of a cutter shaft 5, pivotally mounted on the bow of ship 1, there is mounted a cutter 6 provided with blades adapted to mine peat by cutting a layer of peat l2 and crushing it into small blocks by the rotation of the blades of the cutter. These small blocks are sucked in the form of a slurry together with water in the peat bed through a pipe 8 by means of a pump 9. The cutter 6 is easily movable up and down and to right and left by means of a boom 7. The slurry is fed to the next step by means of a pump 9 through a pipe 11 supported by floats 10. If mud 13 is mined, the quality of the product is badly influenced. Therefore, it is preferable to prevent the cutter 6 from descending 0 too deeply and it can be equipped with a suitable water level gauge to guard against this.

The slurry containing the fibrous and humic components is separated into solid fibrous component containing to percent and a humic suspension containing 0.5 to 5 percent humic component by means of a screen of suitable mesh size. It is preferable that this separation be carried out by the use of separating equipment comprising a rotary cylindrical screen having a rotary axis positioned transversely across the direction of the flow of the slurry and having a screen of a mesh of about 0.5 to about 5 mm. The screen is mounted in a conveying trough provided with a weir which communicates with the interior of the cylindrical screen for overflowing the humic component suspension separated from the mixed slurry. The fibrous component is continuously separated from the humic component while rotating this rotary screen about 5 to about 30 rpm.

The operation of separating the fibrous component from the humic component suspension shall be explained with reference to FIG. 2 wherein the peat slurry 14 is fed from the left in trough 15. A rotary cylinder 16 wrapped with a screen 17 on its periphery is positioned transverse to the direction of flow of the slurry. The size of the meshes of the screen is preferably about 0.5 to about 5 mm. depending on the end use intended for the obtained fibrous and humic components. If it is less than about 0.5 mm., the meshes clog so much as to be not very practicable. If it is more than about 5 mm., a considerable amount of short fibrous component mixes into the fine grain humic component and the separation efficiency drops. Rotating the cylinder at about 5 to about 30 rpm. is useful in preventing the clogging of the meshes, thus maintaining the treating capacity and separation efficiency substantially constant and thereby securing a continuous operation. The rotation also serves to move the fibrous component, accumulated on the surface of the screen and in the bottom part of the trough, past the screen.

The humic component suspension having passed through the meshes moves into the rotary cylinder 16, assumes a constant level and overflows weirs 18 of a fixed height provided in the conveying trough 15. The thus separated humic component slurry 19 is then introduced into a precipitating pool and is recovered as cakes, for example, having a water content of about 80 percent by suitable means such as a super decanter or Oliver filter.

On the other hand, the separated fibrous component 20 is moved through the bottom part of the trough 15 under screen 17 by the rotation of the rotary cylinder and is accumulated on the downstream side of the screen. This fibrous component 20 is scraped up with a fork, is dehydrated with a roll or press to form an intermediate product having a water content of about 50 to about 70 percent and is further heated and dried to obtain a final product. Furthermore, if it is desired to better separate the humic component, additional water may be added to the separated humic suspension and the same treatment as described above repeated to remove additional amountsof the fibrous component.

Since the thus dried fibrous component has a bulk specific gravity of about 0.1, i.e., a bulk density of about 0.1 gram per cc., in transporting it, it is preferable to compress it so that the bulk specific gravity is about 0.3 to about 0.4 i.e., a bulk density of about 0.3 to about 0.4 gram per cc. The fibrous component of peat has the characteristic that its compressibility is at a maximum when the water content is about 20 percent. Furthermore, when it is to be used as an adsorbent for a liquid feed and to keep it from getting moldy during storage, it is particularly preferable to adjust the water content of the product fibrous component to a point in the range of about to about 20 percent.

The thus obtained fibrous component can be used as an adsorbent for liquid feed such as, molasses, soluble fish materials or beef tallow, a fiber board or any other fibrous product. On the other hand, the humic component can be used as a soilconditioning material, a waste water treating material, a deodorant or a fertilizer as an organic substance for accelerating the growth ofcrops.

As a result of the present invention, in separating peat into fibrous and humic components, the operation from peat mining to the recovery of its components can be carried out efficiently throughout. Furthermore, since the separated fibrous component has been separated from the colloid humic component, it can be mechanically dehydrated to a considerably greater degree. The obtained fibrous and humic components can be applied to many uses according to their respective characteristics and thus can be utilized more effectively than when mixed in peat in its natural state.

Examples ofthe present invention are given below.

EXAMPLE 1 Using the apparatus shown in FIG. 1, 300 tons per hour of raw peat (having a water content of 90 percent) were mined under water with a pump dredger and 860 tons per hour of a slurry having about 3.5 percent peat solids were hydraulically conveyed to the surface. One hundred tons per hour of the slurry were passed through a disintegrator or beater having 12 rotary blades 500 mm. long and fitted at right angles with the axis to further disintegrate the peat in the slurry. Then the slurry was flowed against a rotary cylindrical screen having meshes of 1 mm. and rotating at 25 rpm. as shown in FIG. 2 to remove the humic component as an aqueous suspension and obtain about 15 tons/hour of the fibrous component which had a water content of about 85 percent. The fibrous component then was dehydrated with a screw-type dehydrator and passed through an air current dryer, 0.3 meter in diameter and 30 meters long to reduce the water content to about percent. The dried fibrous component was crushed with a crusher and was compressed using a pressure of 40 kglcm. to produce 120 packets per hour of the fibrous product having a bulk specific gravity of 0.35, each packet weighing 20 kg.

The humic component suspension was conveyed to a precipitating pool 5 meters wide, 20 meters long and 2 meters deep and was left to stand for 24 hours. Then a slurry of about 5 percent solids of the humic component which had precipitated at the bottom was sucked up with a pump and the humic component was separated by filtration as cakes having a water content of about 80 percent at a rate of l ton/hour. The cakes were dehydrated with a screw-type dehydrator to a water content of about 55 percent and were then crushed to produce 0.4 ton/hour of the humic product.

EXAMPLE 2 In the same manner as in example I, peat (of a water content of 93 percent) was mined in water with a pump dredger, was hydraulically conveyed as a slurry containing 10 tons of water per ton of the peat, was fed into a trough 60 cm. wide and 40 cm. deep and was separated into the fibrous component and humic component by means of an apparatus as shown in FIG. 2 consisting of a combination of a rotary cylinder mounted in the trough with its rotational axis at right angles across the trough, having a 20-mesh screen wrapped around the entire peripheral surface. The screen was rotating at about 27 rpm. The conveying trough, was provided with weirs in the sides of the trough in a position l2 cm. above the lower part of the periphery of the screen and communicating with the interior of the rotary cylinder. The lower part of the periphery of the screen maintained a clearance of 10 cm. from the bottom of the trough. The cylinder had a diameter of 60 cm. and a length of 60 cm.

e humic component slurry of a concentration of about 0.5 percent obtained by overflowing the weirs was 38 tons per hour and was fed into the precipitating pool described in example l to be recovered.

The fibrous component was obtained at the rate of about 2 tons per hour with a fork from the trough and had a water content of about percent. It was then dehydrated to a water content of about 65 percent with a screw press. The humic component present as mixed in this fibrous component was one-fiftieth of that in the original raw material peat on a weight basis. This fibrous component was further dried to a water content of about 20 percent and was compressed with 40 kg./cm. pressure to form blocks ofa bulk specific gravity of 0.34, each block weighing about 20 kg. Furthermore, when the fibrous component dehydrated with the screw press was disintegrated with the addition of water and again applied to the screen as described above, the amount of the humic component present in the resulting fibrous product was reduced to one twenty-five hundredth that of the raw material peat on a weight basis and a product ofa very high quality was obtained.

What is claimed is:

1. In a method of removing peat from a peat bed and separating it into its fibrous component and its humic component wherein a peat slurry of said peat in the water existing in said peat bed is formed by cutting said peat from said peat bed in the form of small blocks in said water, said peat in said peat slurry is disintegrated to form an aqueous suspension of said fibrous and humic components, and said fibrous component is separated from said humic component, the improvement which comprises flowing said aqueous suspension of said fibrous and humic components against a cylindrical screen which permits said humic component as an aqueous suspension to pass through said screen and bypasses said fibrous component around said screen, said cylindrical screen having meshes of about 0.5 to 5 mm. and rotating at about 5 to 30 rpm, and removing said humic component suspension from within the cylindrical screen.

2. Method as claimed in claim 1 wherein the separated fibrous component is mechanically dehydrated and compressed to a bulk specific gravity of 0.3 to 0.4. 

2. Method as claimed in claim 1 wherein the separated fibrous component is mechanically dehydrated and compressed to a bulk specific gravity of 0.3 to 0.4. 